By Anna M. Phillips, Times Staff Writer Anna M. PhillipsTampa Bay Times In Print: Thursday, August 2, 2012

Tropical Storm Debby swept more sand off of Pinellas County's beaches than any other storm in the past decade, according a report released Wednesday by University of South Florida researchers.

Over the course of three days in June, Debby scrubbed the county's coastline of 630,900 cubic yards of sand, enough to fill about 193 Olympic-sized swimming pools. Already, county officials have estimated that restoring the beaches to their previous state could cost $25 million.

That estimate rose even higher Wednesday as officials added $866,000 to the total, the cost of restoring Fort De Soto beach and Honeymoon Island.

The study by Ping Wang, a University of South Florida geology professor, and doctoral student Tiffany Roberts, found that beaches in the southern barrier islands fared the worst against Debby's southerly winds. The storm pushed sand north, depositing most of it a few feet from shore and creating wide and shallow sand bars.

The hurricane season stretches from June 1 to Nov. 30 and, with more storms on the way, the county's beaches are more vulnerable.

At Pass-a-Grille beach, the dune line retreated by an average of almost 12 feet and the area lost just over 25 feet of beach as its shoreline moved inland. Indian Shores and North Redington, whose beaches that were given sand infusions in 2006, were among the most severely eroded. Both lost about 34 feet of beach. Sunset Beach, rebuilt in 2010, lost about 21 feet.

"For the 11 years that we have been studying the beach along these three barrier islands, Debby is probably the worst," Wang said. "It caused the most widespread beach erosion."

Before Debby, the most destructive storm to hit county beaches was Hurricane Frances, Wang said. In 2004, Frances brought stronger winds to the bay area, but passed more quickly, causing less overall erosion.

As well as tearing up beaches that are critical to the area's economy, Debby also damaged the ongoing beach restoration work on Sand Key. The $31.5million project was in its early stages, said Andy Squires, the county's coastal manager, but by the time it is done, he expects to have about 25 percent less sand there than anticipated.

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Tropical Storm Debby delivered massive losses to Pinellas beaches, USF study says